Pentalene derivatives and their production



United-States Patent Office Patented Jun-e 4, 1958 3,387,017 PENTALENEDERIVATIVES AND THEIR PRODUCTEON Marcel Joseph Celestin Lefort, Lyon,France, assignor to Rhone-Poulenc S.A., Paris, France, a French bodycorporate No Drawing. Filed Get. 15, 1964, Ser. No. 404,158 Claimspriority, application France, Oct. 17, 1963,

6 Claims. (Cl. 260--448.8)

ABSTRACT OF THE DISCLOSURE New silyl-pentalenes, useful as additives fororganesilicone resins and as intermediates in the production ofpentalene, are made by reacting 1,5-cyclooctadiene with atri-substituted silane in the presence of a free radical catalyst.

The present invention provides new derivatives of bicyclo[3.3.0]octane,or pentalene, containing silyl groups, and a process for theirproduction.

These new derivatives have the formula:

where the symbols R are the same or different and represent halogen,e.g. chlorine, hydrocarbon radicals, hydrocarbonoxy radicals, orcarboxylic acyloxy radicals, such as 'alkoxy, cycloalkoxy, aryloxy, oracyloxy radicals, and more especially lower alkyl, lower alkanoyloxy orphenyl. The term lower means that the group in question contains amaximum of 4 carbon atoms. Silicon derivatives of pentalene have notpreviously been described.

According to a feature of the invention, the new compounds are producedby reacting cyclooctadiene l,5 with a trisubstituted silane of formula:HSiR (where R is as hereinbefore defined) in the presence of afree-radical generating catalyst, and isolating a m-onosubstitutedpentalene from the reaction mixture. Where the silane starting materialcontains one or more halogen atoms, one or more of these maysubsequently be replaced by another radical within the definition of R.

For example, the compounds of Formula I where R represents an alkyl,alkenyl, cycl-oalkyl, cycloalkenyl or aryl radical may be made by firstpreparing a compound of Formula I where R represents halogen and thenreacting this compound with a corresponding Grignard reagent. This isespecially appropriate when in the desired compound R is lower alkyl orphenyl.

It is also possible to produce compounds of Formula I where R representsa carboxylic acyloxy radical, especial- 1y lower alkanoyloxy, byreacting an organic carboxylic acid anhydride with ahalogenosilylpentalene.

It is known to react silanes, especially trichlorosilane andtriethylsilane, with cyclooctadiene-1,5 in the presence of platinum onan alumina support (cf. Pike and MoDonagh, J. Chem. Soc. 2831 [1963]);but these workers obtained only the correspondingtrichlorosilylcyclooctene and triethylsilylcyclooctene, and did notobserve any formation of a compound containing an internal bridge. Theformation of such an internal bridge in the process of the invention is,therefore, entirely unexpected.

-The presence of the bicyclo[3.3.0]octane skeleton in the new compoundshas been proved by elementary analysis, the bromine index, which provesthe absence of a double bond, and by nuclear magnetic resonancespectrometry by comparing the resonance spectrum of the new compoundswith that of cyclooctadiene on the one hand and with that of'bicyclo[3.3.0]octanone-2 on the other. While it is not known withabsolute certainty whether the silicon residue is attached in position 2or 3, it is believed to be attached in position 2.

Cyclooctadiene-LS used in the process of the invention is readilyaccessible by dimerizing butadiene.

The silane derivative HSiR may be any compound in which the R groups areidentical, for example, trichlorosilane, triethoxysilane,triacetoxysilane, or triethylsilane, or different, for example,methyldichlorosilane, phenyldichlorosilane, dimethylchlorosilane ormethyldiacetoxysilane.

The free-radical generating catalyst may be any substance that onthermal decomposition furnishes free radicals, e.g. organic peroxides,such as benzoylperoxide and acetylperoxlde, and azodiisobutyronitrile.The reaction can be performed by heating at a temperature from to 250C., more advantageously from to 225 C., or at a lower temperature, e.g.below 100 C., such as room temperature (about 15 C.) if the reaction isperformed in the presence of actinic light or other electromagneticradiation of shorter wavelength, for example radiation of a wavelengthbelow 0.4a, such as ultraviolet radiation or 'y-rays.

The new compounds have a variety of uses. They may be incorporated inorganosilicone resin compositions which are completely compatible withalkyd resins and other polyesters. They act as anti-thixotropizingagents for organosilicone elastomers. They may also be used in themanufacture of pentalene, since, for example, on treatment with sodiumhydroxyole, trimethylsilylpentalene is easily converted intotrimethylsilanol and pentalene.

The following examples illustrate the invention.

Example 1 A 1 litre autoclave is charged with 21 6 g. (2 mols) ofcyclooctadiene-l,5, 2 37 g. (1.76 mols) of trichlorosilane and -10 g.'ofbenzoyl peroxide. The mixture is heated for '42 hours at 200 C. Afterallowing the autoclave to cool, the unreacted trichlorosilane andcyclooctadiene are distilled olf, after which 220 g. of product aredistilled, which has the following characteristics: B.'P.= 123-'125 C./23 mm. Hg or 7475 C./0.9 mm. Hg, and (1 :1232. This product istrichlorosilylpentalene.

Example 2 -A 1 litre autoclave is charged with 2116 g. (2 mols) ofcyclooctadiene-l,5, 202 g. (1.76 mols) of methyldichlorosilane, and 10g. of benzoylperoxide, and the mixture is heated for 66 hours at 200 to205 C. The unreacted m-ethyldichlorosilane and cyclooctadienedfi aredistilled off, and after this 87 g. of a product are obtained which ismethyldichlorosilylpentalene, having the following characteristics:B.=P.=7475 C./ 1.3 mm. Hg, and 1 1.10 2.

Example 3 A Grignard reagent from 36 g. (1.5 gram atoms) of magnesiumand 212 g. (1.5 mols) of methyl iodide in 400 cc. of anhydrous diethylether is added dropwise to 81 g. (0.33 mol) of trichlorosilylpentaleneand the mixture is refluxed for 8 hours. The reaction mixture is thencooled, poured into ice-water, and neutralized with aqueous hydrochloricacid solution. The supernatant liquid is decanted, the organic layerextracted with 2x200 cc. of ether, and the organic extracts are thencombined and the ether removed. On distillation of the residue, thereare obtained 35.3 g. of trimethylsilylpentalene, having the fol-lowingcharacteristics: B.P.=89-90 C./15 mm. Hg, d =0.8648, and n =1.4679.

Example 4 A 250 cc. distillation flask is charged with 48.7 g. (0.2 mol)of trichlorosilylpentalene and 67 g. of acetic anhyclride. The mixtureis slowly heated and the theoretical amount of acetyl chloride iscollected. The excess acetic anhydride is then removed by distillation,and the residue is distilled to yield 31 g. of triacetoxysilylpentalene,having the following characteristics: B.P.=114 C./ 0.07 mm. Hg, and d8":1.1419.

Example 5 A 1 litre autoclave is charged with 108 g. (1 mol) ofcyclooctadiene-1,5, 118 g. (0.66 mol) of phenyldichlorosilane, and 5 g.of benzoylperoxide, and the mixture is heated for 18 hours at 198 to 200C. After the unreacted phenyl-dichlorosilane and cyclooctadiene havebeen distilled off, 39 g. of (phenyldichlorosilyl)-pentalene areobtained, having the following characteristics: B.P. l29130' C./0.45 mm.Hg, and d =1.1860.

Example 6 A 1 litre autoclave is charged with 147 g. (1.3 mols) ofcyclo0ctadiene-l,5, 135 g. (1 mol) of trichlorosilane and 5 g. ofazodiisobutyronitrile, and the mixture is heated for 44 hours at 195 to200 C. After the unreacted trichlorosilane and cyclooctadiene have beendistilled off 93.5 g. of (trichlorosilyl)-pentalene, boiling at 123-125C. under a pressure of 16 mm. Hg are obtained.

Example 7 A 3 litre flask, carrying a reflux condenser and equipped witha quartz tube in which is an ultraviolet lamp dipping into the oentre ofthe flask, is charged with 903 g. (6.7 mols) of trichlo-rosilane, 60 g.(0.55 mol) of cyclooctadiene-1,5 and 2.7 g. of benzoyl peroxide.

wherein each of the symbols R is chlorine, lower alkyl, loweralkanoyloxy, or phenyl.

. Trichlorosilylpentalene.

. Methyldichlorosilylpentalene.

. Trimethylsilylpentalene.

. Triacetoxysilylpentalene. Phenyldichlorosilylpentalene.

References Cited UNITED STATES PATENTS 2,762,823 9/1956 Speier 260448.2H2,872,471 2/1959 Ramsden et al. 260-448.2H 3,188,336 6/1965 Haszeldine260-448.2 3,256,333 6/1966 Dowbenko 204-158 XR 3,290,359 12/1966 Mark260-4482 XR TOBIAS E. LEVQW,

P. F. SHAVER, Assistant Examiner.

Primary Examiner.

